Alpine ski touring bindings allow the heel of the user's footwear to be latched to a ski or other snow travel aid for sliding downhill (the “downhill mode”) and allow the heel to be released for walking and climbing (the “touring mode”). Thus, the binding allows for selective holding of the footwear heel to the snow travel aid so that the user may select between the downhill mode and the touring mode. Modern alpine ski touring bindings allow the footwear to release from the snow travel aid when in the downhill mode, in case of a fall. When in the touring mode, the user may climb or walk with a great degree of freedom since the footwear is pivotally engaged with the aid near the toe of the footwear while the heel of the footwear is free to move upward and downward relative to the aid. A historical collection of such bindings can be viewed in the “Virtual Museum of Backcountry Skiing Bindings” at www.wildsnow.com, authored by Louis Dawson.
Alpine ski touring bindings of the type that originated under the brand DYNAFIT are bindings that take advantage of the fact that modern alpine touring footwear has a rigid sole. Thus, it is unnecessary to provide a bar, plate or other arrangement connecting toe and heel units, as is the case with many other alpine touring bindings. This type of binding is referred to herein as a “Tech-type” binding. Examples of such bindings are disclosed in patent publications AT 402020, EP0199098, EP0519243, EP1559457, WO2009/105866, WO2009/121187, and US2015/0014963.
Tech-type binding systems comprise toe and heel units that function independently to retain the footwear toe and heel respectively on a snow travel aid. The toe unit typically comprises a set of jaws that pivotally engage inserts placed in the footwear toe region during manufacture of the footwear. The toe unit is mounted at an appropriate location on the upper surface of the snow travel aid. The heel unit is mounted rearward of the toe unit at a location typically indicated by the length of the footwear sole.
The heel unit of a Tech-type binding comprises one or more forward connectors (typically a pair of pins) which extend forward to engage a fitting typically placed in the heel of the footwear during manufacture of the footwear. Under forward (My) release conditions during a fall, the pins are forced apart against a resistant, lateral force which allows the pins to disengage from the fitting in the footwear heel. The pins typically communicate with one or more My springs through components that include a sliding wedge arrangement, one or more cams or other suitable means for translating forwardly directed pressure exerted by the My spring(s) into a lateral force that resists the pins moving apart from each other. Forward release values are adjusted by adjusting pre-load compression on the My spring. In the heel unit disclosed in DE102011078834, the ends of a “U”-shaped bracket serve as pins for connecting to a Tech-type fitting in the footwear heel while the web of the bracket provides the lateral force that resists separation of the pins. This eliminates the need for a separate My spring but does not provide for readily adjustable forward release values.
The heel unit of a Tech-type type binding also provides for lateral (Mz) release in the case of a fall and can further allow for transition between downhill and touring modes as a result of the body of the heel unit being pivotally engaged on a support. Variable lateral release values are provided by adjusting the pre-load compression of an Mz spring that is separate from the My spring and which presses a plunger or other bearing element against a flat or hollow region on a surface of a support on which the body rotates. By providing a plurality of such regions around the perimeter of the support, the body of the heel unit will tend to rest at different rotational positions corresponding to each flat or hollow region on the support, which facilitates retention of the heel unit in either the downhill or touring mode. To switch between touring and downhill modes with such a system, the heel unit is rotated so that the forward connector(s) are positioned to engage the footwear heel (downhill mode) or so that the connector(s) face away from the heel (touring mode). When the forward connector(s) face away, the footwear heel is free to move upward and downward to facilitate walking and climbing with the toe of the footwear pivotally retained on the snow travel aid by means of the toe unit. Some Tech-type heel units rotate to facilitate lateral release but not for transition between downhill and touring modes. For example, embodiments disclosed in WO2009/105866 rotate for lateral release and translate longitudinally to transition between downhill and touring modes.
A touring binding heel unit that provides a single point of adjustment for forward and lateral release is disclosed in EP0519243. That heel unit does not use the forward connectors of a binding heel unit that disengages from a Tech-type fitting in the heel of the footwear through movement of forward connectors themselves. Instead, the parts of the heel unit in EP0519243 that engage with the heel are fixed relative to the heel unit and disengagement from the heel results from vertical and rearward displacement of those elements caused by rotational movement of the entire body of the heel unit about a horizontal axis perpendicular to the direction of travel. The body also rotates on a vertical axis to provide lateral release and transition between downhill and touring modes. A single spring applies pressing force through a member that presses against a complex series of recesses formed about a spherical support member. The design of this binding is not conducive to providing a lightweight variant of a Tech-type heel unit nor is it intended to cooperate with footwear that has been manufactured to contain typical Tech-type fittings in the heel.
Both simplicity and minimizing weight are desirable characteristics of a touring binding. The heel unit disclosed in EP2384794 is based on a traditional Tech-type binding with pins that engage Tech-type fittings in the heel of the footwear and which separate against a resistant force provided by a My spring for forward release. Rather than including a separate Mz spring and associated components for transmitting force against the support on which the body of the heel unit rotates, a My spring under compression and fixed at its rearward end provides the force to resist both forward release as well as to resist rotation of the body. Adjustment of pre-load compression on the single spring adjusts Mz and My release values simultaneously. This is made possible by transferring pressure from the forward end of the My spring directly through a vertically arranged follower that presses against a cam surface within a depression located at the rear of the rotational support for the body of the heel unit as well as to the pins that engage the fitting in the heel of the footwear. Lateral forces exerted on this heel unit when in the downhill mode result in the body rotating against resistant force as usual. However, since the Mz components are also coupled to the My spring, such movement simultaneously relieves the resistant force exerted on the pins through the My components. This is not desirable if the device were to be adjusted or configured such that lateral shocks insufficient to cause lateral release would nevertheless allow the footwear to disengage from the heel unit in a forward direction without resistance.